Boat



Oct. 25, 1938. G. M. HOFFMAN BOAT Filed Sepi. 26, 1955' 2 Sheets-Sheet l INVENTOR.

ATTORNEY? Oct. 25, 1938.

G. M. HOFFMAN BOAT Filed Sept. 26, 1935 2 Sheets-Sheet 2 BY /%Z;%W ATTORNEYI Patented Oct. 25, 1938 I BOAT George M. Hoffman,- Upper Montclair, N. J.; Ruth T. Hoffman administratrix of said George M. Hoffman, deceased Application September 26, 1935, Serial No. 42,255

The necessity of having shallow draft for tow drawings, it is understood that a different num- 5 boats has restricted the size of the propelling ber may be used if desired. The portions of the means resulting in low efficiency due tothe fact shafts 4, 4' extending to the rear of the hull of that the propelling means was required to imthe boat are supported by cantilevers 5 which are part an uneconomical velocity to the water rigidly connected to the hull of the boat or may stream that was thrust astern in order to absorb be made integral therewith when the hull is made 10 the power of the engine or motor that was inof steel. The cantilevers 5 carry bearings for stalled for driving the boat. The cross section the shafts 4, 4 and these shafts are preferably of the stream of water that was thrust astern by installed at or near the water line so that the prior boats of this sort was only about half of propellers 3, 3' are about half submerged.

that of the immersed cross section of the boats, The boat may be provided with rudders 6 of 15 although it has been known for a long time that the conventional sort, but since these'rudders and for economical propulsion a much larger cross the operating mechanism therefor constitute no section of the water stream thrust astern was part of this invention they'are not described in needed. detail.

o Attempts have been made to increase the An after-deck 8 is installed above the propellers volume of water that could be thrust astern with 3, 3 upon cantilever supports 9 which may expropeller driven boats by immersing the propellers tend from side and center trusses of the boat 5. for about two thirds of their diameters and in- Tilting tunnels l0, II! are installed above the. stalling tunnels over the propellers whose sides propellers 3 and 3' in such positions that solid and ends extended below the water-line so as water will be provided for the propellers as water to provide solid water for the propellers; The is lifted and thrust astern by the propellers. 25 reaction of the stream of water against the after- Journals II are provided for the tunnels end of such tunnels which had to extend below athwartship so that'the ends thereof tilt up and the water-line in order to enable the boats to be down. The upper wall l2 of each tunnel is con- 0 propelled backwards produced drag which intercave on its lower side or extends downwardly from .1 fered greatly with the efficiency during forward its middle to its opposite ends, and the side walls travel of such boats. Even providing a flap for I3 thereof extend "below the water line and terthe tunnel was not successful because of troubles minate in thin edge the s of the nn s be with drift accumulations and also unsatisfactory left open.

maneuvering and backing ability of boats The inside walls of each tunnel converge toward equipped with such tunnels. the middle to provide a Venturi'section M where By the present invention propeller-driven boats the propeller is located when the tunnel is in of shallow draft can be produced that have high place. r efficiency, ease of manipulation and cause water Cross bars or straps l5, I6 are provided on 40 streams of cross section comparable in size, or the after-deck to limit theextent of tilting of 1 approximating the size of the immersed cross seethe tunnels as the ends of the tunnels strike the tion of the boat to be thrust astern. under-sides of these cross bars in the extreme The invention will be understood from the depositions of the tunnel. It has been found satisscription in connection with the accompanying factory to pivot the tunnels and provide stops in drawings in Which 1 a p a w Of all such positions that the tunnels can tilt through 4 illustrative embodiment of the invention; Fig. 2 an angle of about 13 fol-e and aft from its n is a side v w of h same; F 3 i a si vi w zontal position. Rollers H are provided along n n enl r ed scale showin a tunn l in the forthe sides of the openings in the afterdeck 8' in ward moving position of the boat; Fig. 4 is a simiwhich the tunnelsare located so as to guide the 50 lar View in longitudinal section showing the tunnels and make it easy for the same to be 50 tunnel in a backward moving on; i 5 turned. Atow line (not shown) may be attached is an end View Of 1 n an ar ed S ale; to the afterdeck 8, or other portion of the boat Fig. 6 is an end view similar to Fig. 5 on an enin any convenient way. v I l d scale with p r r mov d; Fig- 7 s a plan Sluiceways l8 -and I8 are r vided in the view of the lower side of one of the tunnels on stem of the boat on opposite sides thereof 10-' 55 an enlarged scale; Fig. 8 is a section along the cated in positions to receive the discharge of line bb of Fig. 7 and Fig. 9 is a section along water from the propellers 3 and 3, respectively, the line c-c of Fig. 7. when the propellers are driven backwards. The

In the drawings reference character I indicates end walls IQ of the sluiceways I 8 and I8 ex- 0 a tow boat having a flat bottom and small draft. tend diagonally from near the center line of the 11 Claims.

This invention relates to boats and more particularly to boats for inland navigation, such as shallow draft tow boats, for example, that are propeller driven.

Driving means 2, 2 are somewhat diagrammatically indicated for driving the propellers 3, 3' through shafts 4, 4. Although only two propellers and driving motors'are indicated in the boat to opposite edges thereof, and the bottom walls or floors 20 of these sluiceways are at or above the water-line of the boat. When only one propeller is used one sluiceway maybe provided, with the propeller located along the center line of the boat the sluiceway extending diagonally from one side of the center line of the boat to the edge so that water from the propeller will be discharged into it, or two diagonal sluiceways may be provided leading from each side of the center line with a movable plate pivoted on the center line so as to divert the water into either sluiceway or part into one. and part into 'the other.

In operation when the boat is being driven forward the streams of water from the propellers 3 and 3 striking the rear portions of the upper walls of the tunnels l tilt the same into the position shown in Fig. 3 with the front portion of the upper wall of the tunnels forming a smooth passage for flow of water from the bottom sloping, rear portion of the boat to the propellers. The raised rear ends of the tunnels or the tilting upwardly of the discharge ends of these tunnels permit free, discharge of water without interposing a drag reaction that occurs with fixed tunnels, thus eliminating losses due to interference with free flow. At the same time the edges ,of the sides of the tunnels extending below the water-line and the forward straight edges of the tunnel which conform with the rearportion of the hull and fits against it, together with the seal of water from the stern wave provide sealedclosures so that the suction is not broken and solid water is secured for the propellers. When the propellers are reversed the tunnels automatically tilt in the opposite direction to the position shownin 4 so that there is a smooth flow of water toward the boat and a portion of this water is discharged into diverging sluiceways l8 without causing great drag reaction or resistance to backward travel of the boat. Besides, the weight of water discharged into sluiceways l8 aid in causing the rear end of the boat to squat and keep the rear ends of the tunnels l0 below the. water line. The side thrust of the streams of water entering the tunnels balance each other and the water is discharged from these streams above the water line.

By running one of the propellers in one direction and the other in the other direction the boat can be turned as sharply as desired and can even be made to pivot, and by running only one propeller backwards the reaction produced by the stream in one sluiceway very effectively turns the boat, thus facilitating manuevering of the boat.

I claim:

1. A boat having a propeller that is located partially above the water line and means forming a tilting tunnel over said propeller having edges extending below the water line, saidmeans narrowing from its ends towards its middle portion and having its narrowest portion near its center.

2. A boat having a propeller and a sluiceway in said boat into which water of the slip stream from said propeller may be discharged said sluiceway having one side open. v

3. A boat having a propeller and a sluiceway in said boat located above the water line into which water of the slip stream from said propeller may be discharged said sluiceway having one side open.

4. A boat having a propeller and a sluiceway in said boat into which water from said propeller may be discharged, and means for guiding water of the slip stream from said propeller into said sluiceway said sluiceway having one side open.

5. A boat having a propeller and a sluiceway in said boat into which water from said propeller "may be discharged, and means for guiding water from said propeller into said sluiceway, said means comprising a tilting tunnel located over said propeller.

6. A boat having a propeller and a sluiceway in said boat into which water from said propeller may be discharged, and means for guiding water from said propeller into said sluiceway, said means comprising a tilting tunnel journalled athwartship over said propeller.

'7. A boat having apropeller and a sluiceway in said boat into which water from said propeller may be discharged, means for guiding water from said propeller into said sluiceway, said means comprising a tilting tunnel located over said propeller, and means to limit the extent to which said tunnel tilts.

8. A boat having propellers located on opposite sides of the center line of said boat partially above the water line, and tilting tunnels above said propellers, and means to cause the rear end of said tunnels to extend below the water line when said propellers are running backwards and above the water line when said propellers are running forwards.

9. A boat having propellers located on opposite sides of the center line of said boat partially above the water line, and tilting tunnels above said propellers, said boat having sluiceways along its sides to receive water from said propellers.

10. A propulsion mechanism for a boat having a propeller that is normally located partially above the water line, comprising a structure U-shaped in cross-section pivotally mounted on said boat substantially mid-way of the length of said structure and overlying said propeller and its shaft and the side edges extending below the water line on both sides of the pivotal axis, said pivotal axis being substantially at a right angle to said propeller shaft, said U-shaped structure defining a tunnel with its surfaces so constructed and shaped that it will automatically pivot on the pivotal mounting whereby the propulsive thrust will not adversely affect propulsion of the boat upon reversal of the direction of rotation of said propeller.

11. A propulsion mechanism for a boat having a propeller that is normally located partially above the water line, comprising a structure U-shaped in cross-section pivotally mounted on said boat substantially mid-way of the length of said structure and overlying said propeller and its shaft and the side edges extending below the water line on both sides of the pivotal axis, said pivotal axis being substantially at a right angle to said propeller shaft, said U-shaped structure defining a tunnel with its surfaces so constructed and shaped that it will automatically pivot on the pivotal mounting whereby the propulsive thrust will not adversely affect propulsion of the boat upon reversal of the direction of rotation of said propeller, the rear end of said U-shaped structure extending below the water line when said propeller is running backwards.

GEORGE M. HOFFMAN. 

